Freezing point lowering compositions are in widespread use for a variety of purposes, especially to reduce the freezing point of an aqueous system so that ice cannot be formed or to melt formed ice. Generally, freezing point lowering compositions depend for their effectiveness upon the molar freezing point lowering effect, the number of ionic species that are made available and the degree to which the compositions can be dispersed in the liquid phase in which the formation of ice is to be precluded and/or ice is to be melted.
The most pervasive of the commonly used products for deicing are common salt, calcium chloride, magnesium chloride and urea, with common salt (sodium chloride) being the least expensive and most commonly used. Common salt widely is used to melt ice on road surfaces and the like. In this manner, the salt forms a solution with the available liquid in contact with the ice and thereby forms a solution with a lower freezing point than the ice itself so that the ice is melted. Chloride salts, however, suffer from relatively severe drawbacks, such as the harmful effects on surrounding vegetation by preventing water absorption in the root systems, the corrosive effects on animal skin, such as the feet of animals, clothing, roadways and motor vehicles, and the deleterious effects on surface and ground water. Thus, any new method of deicing or new deicing composition that can reduce the amount of chloride salts, or eliminate chloride salts entirely, would solve a long felt need in the art.
Other inorganic salts also are known to be useful as freezing point lowering agents such as, potassium phosphates, sodium phosphates, ammonium phosphates, ammonium nitrates, alkaline earth nitrates, magnesium nitrate, ammonium sulfate and alkali sulfates.
Another drawback of certain prior art deicing fluids is their high chemical and biological oxygen demands, which make them environmentally unfavorable. The glycols are exemplary of deicing fluids that particularly suffer from this type of environmental drawback. Thus, any new method of deicing or new deicing composition that can reduce the chemical or short term biological oxygen demands also would solve a long felt need in the art.
Typical aqueous solutions of low freezing point deicing and anti-icing agents include chloride salt brines, ethylene glycol and propylene glycol solutions. The use of chloride brines in anti-icing compounds can reduce, although not eliminate, the impacts of chlorides when applied as solids for deicing. Brines and glycol solutions also are employed as components of fluids used to transfer heat in applications where the fluid may be exposed to temperatures below the normal freezing point of water as well as components of drilling fluids employed in oil and gas operations. Ethylene glycol solutions are well known for use as coolants for automobiles and the like in regions where the temperature may fall below the normal freezing point of water. Ethylene and propylene glycols are used in relatively large quantities at major airports in northern climates in order to keep air traffic flowing during inclement weather. The fluids generally are applied to the wings, fuselage and tail of aircraft and in some instances to the runways to remove ice. Glycols also are employed as hydraulic fluids. However, as mentioned above, these glycol compounds likewise have environmental drawbacks and can be detrimental to aquatic life and to sewage treatment processes.
Other prior art deicing fluids, such as mono and polyhydric alcohols, have toxic effects and high volatility particularly in the low molecular weight range. Further, some of these may be the cause of offensive smells and fire danger. Furthermore, mono- and polyhydric alcohols oxidize in the presence of atmospheric oxygen to form acids, which can increase corrosion of materials.
Due to the problems associated with deicing agents as described above there have been attempts to discover even more deicing agents. For, example, Kaes, U.S. Pat. No. 4,448,702 discloses the use of a freezing-point lowering composition and method that calls for the addition of a water soluble salt of at least one dicarboxylic acid having at least three carbon atoms, such as a sodium, potassium, ammonium or organoamine salt of adipic, glutaric, succinic or malonic acid.
Peel, U.S. Pat. No. 4,746,449, teaches the preparation of a deicing agent comprising 12-75% acetate salts, trace-36% carbonate salts, 1-24% formate salts and 1-32% pseudolactate salts that is prepared from a pulp mill black liquor by fractionating the black liquor into a low molecular weight fraction and concentrating the collected low molecular weight fraction to produce the deicing agent.
U.S. Pat. No. 4,960,531 teaches that small amounts of methyl glucosides, i.e., less than 10%, can be employed as a trigger to conventional salt deicers.
Back et al., U.S. Pat. No. 5,993,684, teach the use of non potassium, non-nitrogen organic salts having a molecular weight less than 201 in anti-icing or deicing applications, but does not teach the use of by-product streams from industrial or fermentation processes. Further, Back teaches against the inclusion of potassium and halide salts or the use of glycol in formulations.
Parks et al., U.S. Pat. No. 4,501,775, teach the use of compositions comprising low concentrations of carboxylic acids, for the specific purpose of application to coal and mineral ores to insure that any ice formed thereon is physically weak and will not deter the unloading of the coal or mineral ores. Further, Parks et al. do not teach the use of by-product streams from industrial or fermentation processes.
Roe, U.S. Pat. No. 4,426,409, teaches the use of organic salts, in formulations for the purpose, as in Parks et al. above, of reducing the cohesive strength of particles when frozen. Further, Roe does not teach the use of by-product steams from industrial and fermentation processes.
Koefod, U.S. Pat. No. 5,531,931, teaches the use of low concentrations of water-soluble organic salts selected from the group consisting of gluconate salts, ascorbate salts, tartrate salts and saccharate salts in combination with water-soluble rare earth salts as agents to reduce the corrosive effects of chloride salts.
Special mention also is made of the Sapienza patents, U.S. Pat. Nos. 5,876,621, 5,980,774, 6,129,857, 6,315,919 and 6,506,318, which disclose especially useful deicing and anti-icing compositions (each of these references is incorporated herein by reference).
Mention also is made of a number of other patents that employ industrial process streams in preparing deicing and/or anti-icing compositions. Examples of such patents are Bloomer, U.S. Pat. No. 6,080,330 (desugared sugar beet molasses); Toth et al., U.S. Pat. No. 4,676,918 (alcohol distilling waste); Janke et al., U.S. Pat. No. 5,709,812 (whey); Janke et al., U.S. Pat. No. 5,709,813 (vintner's condensed solubles); Janke et al., U.S. Pat. No. 5,635,101 (corn wet milling process by-products); Bytnar, U.S. Pat. No. 6,468,442 (corn syrup); and Hartley et al., U.S. Pat. No. 6,299,793 (corn syrup).
However, there still exists in the art a need for further improved deicing and/or anti-icing compositions and methods, which are environmentally benign and/or reduce detrimental environmental effects and that are relatively inexpensive to obtain. Preferably, these new and improved compositions are free of or reduce the use of inorganic salts, are more environmentally benign and are prepared from relatively inexpensive raw materials while still possessing desirable freezing point depression properties. Likewise, there also exists a need in the art for new deicing and/or anti-icing agents that can be used in combination with prior art deicing agents such as inorganic salts or glycols, to substantially reduce the amount of inorganic salts or glycols needed to accomplish the deicing/anti-icing objectives, and thereby concomitantly reduce the detrimental environmental effects of the salts and/or glycols. Surprisingly, the present inventors have found that compositions disclosed herein meet these needs while facilitating by-product disposition from production of hydroxycarboxylic acids and of polymers based upon renewable resources. Production of biodegradable polymers from agriculturally derived sources such as lactic acid is an important strategy to reduce dependence on fossil hydrocarbons for petrochemical feedstocks, and providing a means for achieving economic value from by-product and off specification streams of these processes is an important element in achieving reasonable production economics.